Fix for data race in generating request ids #12
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This fixes a bug where calling random.Int31() from multiple go routines generates a race condition.
The problem is:
==================
WARNING: DATA RACE
Read at 0x00c420027460 by goroutine 281:
math/rand.(*rngSource).Int63()
/usr/local/Cellar/go/1.7.3/libexec/src/math/rand/rng.go:243 +0x156
math/rand.(*Rand).Int63()
/usr/local/Cellar/go/1.7.3/libexec/src/math/rand/rand.go:64 +0x51
math/rand.(*Rand).Int31()
/usr/local/Cellar/go/1.7.3/libexec/src/math/rand/rand.go:70 +0x38
github.com/k-sone/snmpgo.genRequestId()
/Users/whoami/Desktop/code/golang/src/github.com/k-sone/snmpgo/util.go:26 +0x66
github.com/k-sone/snmpgo.(*messageProcessingV1).PrepareOutgoingMessage()
/Users/whoami/Desktop/code/golang/src/github.com/k-sone/snmpgo/mprocessing.go:33 +0x87
github.com/k-sone/snmpgo.(*snmpEngine).SendPdu()
/Users/whoami/Desktop/code/golang/src/github.com/k-sone/snmpgo/engine.go:21 +0xfe
github.com/k-sone/snmpgo.(*SNMP).sendPdu.func1()
/Users/whoami/Desktop/code/golang/src/github.com/k-sone/snmpgo/client.go:320 +0xf2
github.com/k-sone/snmpgo.retry()
/Users/whoami/Desktop/code/golang/src/github.com/k-sone/snmpgo/util.go:56 +0x6d
github.com/k-sone/snmpgo.(*SNMP).sendPdu()
/Users/whoami/Desktop/code/golang/src/github.com/k-sone/snmpgo/client.go:322 +0x19d
github.com/k-sone/snmpgo.(*SNMP).GetRequest()
/Users/whoami/Desktop/code/golang/src/github.com/k-sone/snmpgo/client.go:162 +0xb3
...
Previous write at 0x00c420027460 by goroutine 13:
math/rand.(*rngSource).Int63()
/usr/local/Cellar/go/1.7.3/libexec/src/math/rand/rng.go:244 +0x1be
math/rand.(*Rand).Int63()
/usr/local/Cellar/go/1.7.3/libexec/src/math/rand/rand.go:64 +0x51
math/rand.(*Rand).Int31()
/usr/local/Cellar/go/1.7.3/libexec/src/math/rand/rand.go:70 +0x38
github.com/k-sone/snmpgo.genRequestId()
/Users/whoami/Desktop/code/golang/src/github.com/k-sone/snmpgo/util.go:26 +0x66
github.com/k-sone/snmpgo.(*messageProcessingV1).PrepareOutgoingMessage()
/Users/whoami/Desktop/code/golang/src/github.com/k-sone/snmpgo/mprocessing.go:33 +0x87
github.com/k-sone/snmpgo.(*snmpEngine).SendPdu()
/Users/whoami/Desktop/code/golang/src/github.com/k-sone/snmpgo/engine.go:21 +0xfe
github.com/k-sone/snmpgo.(*SNMP).sendPdu.func1()
/Users/whoami/Desktop/code/golang/src/github.com/k-sone/snmpgo/client.go:320 +0xf2
github.com/k-sone/snmpgo.retry()
/Users/whoami/Desktop/code/golang/src/github.com/k-sone/snmpgo/util.go:56 +0x6d
github.com/k-sone/snmpgo.(*SNMP).sendPdu()
/Users/whoami/Desktop/code/golang/src/github.com/k-sone/snmpgo/client.go:322 +0x19d
github.com/k-sone/snmpgo.(*SNMP).GetRequest()
/Users/whoami/Desktop/code/golang/src/github.com/k-sone/snmpgo/client.go:162 +0xb3
....
Goroutine 281 (running) created at:
...
Goroutine 13 (running) created at:
...
It is generated by do something similar to the following:
for ip := network.CIDR.IP.Mask(network.CIDR.Net.Mask);
network.CIDR.Net.Contains(ip);
IncrementIP(ip) {
go func(dupip net.IP) {
QuerySNMP(ip)
}(ip)
}
Putting a mutex around calls to rand.Int31() solves this issue.